Not Applicable
1. Field of the Invention
The present invention relates to a golf club striking plate. More specifically, the present invention relates to a golf ball striking plate having a variable thickness.
2. Description of the Related Art
Present golf clubs have repositioned weight in order to lower the center of gravity for better performance. This repositioning of weight has for the most part attempted to thin the crown and striking plate of the golf club while precisely placing the weight in the sole of the golf club. However, thinning the striking plate too much may lead to failure of the golf club.
When the striking plate impacts a golf ball during a swing, large impact forces (in excess of 2000 pounds) are produced thereby loading the striking plate. In the relatively thin striking plates of hollow metal woods and cavity-back irons, these forces tend to produce large internal stresses in the striking plate. These internal stresses often cause catastrophic material cracking which leads to failure of the club head.
Computational and experimental studies on hollow metal woods and cavity-backed irons have demonstrated that such catastrophic material cracking most often occurs at impact points on the striking plate. These impact points require added strength to prevent club head failure.
In designing golf club heads, the striking plate must be structurally adequate to withstand large repeated forces such as those associated with impacting a golf ball at high speeds. Such structural adequacy may be achieved by increasing the striking plate stiffness so that the stress levels are below the critical stress. levels of the material used in the striking plate. Typically, for metal woods, the striking plates are stiffened by uniformly increasing the thickness of the striking plate and/or by adding one or more ribs to the interior surface of the striking plate.
Uniformly increasing the thickness of the striking plate portion typically requires the addition of large amounts of material to adequately reduce the stress sufficient to prevent impact and/or fatigue cracking. However, the addition of such a large amount of material to a striking plate generally adversely affects the performance of the golf club.
One of the first patents to disclose variable face thickness was U.S. Pat. No. 5,318,300 to Schmidt et al., for a Metal Wood Golf Club With Variable Faceplate Thickness which was filed on Nov. 2, 1992. Schmidt et al discloses thickening the faceplate to prevent cracking.
A more further disclosure of variable face thickness is disclosed in U.S. Pat. No. 5,830,084 to Kosmatka for a Contoured Golf Club Face which was filed on Oct. 23, 1996. Kosmatka addresses contouring the face to thicken certain regions while thinning other regions depending on the stress load experienced by such regions. Kosmatka also discloses a method for designing a face plate according to measured stress levels experienced during impact with a golf ball. Kosmatka, U.S. Pat. No. 5,971,868 for a Contoured Back Surface Of Golf Club Face, filed on Nov. 18, 1997, discloses similar contouring for an iron.
A more recent disclosure is Noble et al., U.S. Pat. No. 5,954,596, for a Golf Club Head With Reinforced Front Wall, which was filed on Dec. 4, 1997. Noble et al. discloses a face plate with the thickness portion at the geometric center, and gradually decreasing toward the top and bottom, and the sole and heel. The top and bottom ends along a line through geometric center have the same thickness, and the heel and sole ends along a line through geometric center have the same thickness.
Other references make partial disclosure of varying face thickness. One example is FIG. 8 of U.S. Pat. No. 5,505,453 which illustrates an interior surface of a face with a bulging center and decreasing thickness towards the heel and sole ends, similar to Noble et al. Another example is FIGS. 4C and 4D of U.S. Pat. No. 5,346,216 which discloses a bulging center that decreases in thickness toward the heel and sole ends, and the top and bottom end of the face, similar to Noble et al. However, the prior art has failed to design a striking plate or face plate that varies the thickness according to predicted golf ball impact points on the striking plate.
The present invention is directed at a striking plate for a golf club head that is contoured according to the probability of impact with a golf ball in order to lessen the overall thickness of the striking plate, and thus lessen the weight of the golf club head. Further, the striking plate has elliptical regions of varying thickness that allows for more compliance during impact with a golf ball.
One aspect of the present invention is a golf club head having a body with a crown, a sole, a heel end, a toe end and a striking plate. The striking plate has a plurality of elliptical regions of varying thickness. A central elliptical region has a base thickness. A first concentric elliptical region encompassing the central elliptical region and has a first thickness that is thinner than the base thickness. A second concentric elliptical region has a second thickness that is thinner than the first thickness. A third concentric region has a third thickness that is thinner than the second thickness.
The central elliptical region may have a thickness of at least 0.110 inches. Alternatively, the central elliptical region may have a thickness of less than 0.125 inches. The striking plate may be composed of a material selected from the group consisting of titanium, titanium alloys, steels, vitreous metals, ceramics, composites, carbon materials, carbon fiber materials, other fibrous materials and mixtures thereof. The central elliptical region and each of the plurality of concentric elliptical regions may have a thickness range of 0.005 inches wherein the central elliptical region has a thickness range of 0.115 to 0.110 inches and the first concentric elliptical region of the plurality of concentric elliptical regions has a thickness range of 0.110 to 0.105 inches.
The striking plate may further includes heel and toe regions outside the circumference of the plurality of elliptical regions. A first heel end region and a first toe end region may each have a fourth thickness range that is less than the third thickness range. A second heel end region and a second toe end region may have a fifth thickness range that is less than the fourth thickness range. A third toe end region may have a sixth thickness range that is less than the fifth thickness range and a third heel end region may have a seventh thickness range that is greater than the base thickness. The third heel region is adjacent the heel end of the golf club head, and the third toe region is adjacent the toe end of the golf club head. The first and second heel and toe regions are intermediate the third toe and heel regions and the plurality of elliptical regions.
Another aspect of the present invention is a striking plate having a central elliptical region and plurality of concentric elliptical regions encompassing the central elliptical region. Each of the plurality of concentric elliptical regions has a thickness range that is thinner than the thickness range of the central elliptical region. The central elliptical region and each of the plurality of concentric elliptical regions may be angled downward toward the heel end of the sole.
Another aspect of the present invention is a striking plate having a plurality of elliptical regions. Each of the plurality of elliptical regions having a thickness range that is different than the other plurality of elliptical regions wherein the elliptical regions are designed to correspond in thickness to points on the striking plate having the highest probability of impact with a golf ball. Yet another aspect of the present invention is a method for designing a striking plate for a golf club head. The method includes assigning elliptical regions of varying thickness to areas of the striking plate according to the probability of impacts with a golf ball wherein the elliptical region with the highest probability of impacts with a golf ball is the thickest portion of the elliptical regions of the striking plate.
Having briefly described the present invention, the above and further objects, features and advantages thereof will be recognized by those skilled in the pertinent art from the following detailed description of the invention when taken in conjunction with the accompanying drawings.